Homogeneous Carbon Capture and Catalytic Hydrogenation: Toward a Chemical Hydrogen Battery System

Abstract

Recent developments of CO 2 capture and subsequent catalytic hydrogenation to C1 products are discussed and evaluated in this Perspective. Such processes can become a crucial part of a more sustainable energy economy in the future. The individual steps of this catalytic carbon capture and usage (CCU) approach also provide the basis for chemical hydrogen batteries. Here, specifically the reversible CO 2 /formic acid (or bicarbonate/formate salts) system is presented, and the utilized catalysts are discussed.

Toward a Hydrogen Economy: Development of Heterogeneous Catalysts for Chemical Hydrogen Storage and Release Reactions

“…75 On the other hand, one of the concerns in the application of the formate/bicarbonate couple is the solubility of the corresponding salts. For example, the molar solubilities (mol salt in 100 90,121 This solubility likely affects the amount of H 2 uptake and thereby is an important factor for the hydrogen density achievable for the overall reaction system.…”

“…Following such concepts, chemical hydrogen batteries based on CO 2 or bicarbonates have been developed. As representatives, the hydrogen storage and release based on interconversion of CO 2 (or bicarbonate) and FA (or formate) has been established utilizing homogeneous catalysts, ,,− especially applying noble metals Rh, , Ru, − and Ir − and base metals Ni, Fe, , and Mn . Corresponding applications based on CO 2 /FA and bicarbonate/​formate salts promoted by heterogeneous catalysts are summarized in Figure and Figure , respectively.…”

“…On the other hand, one of the concerns in the application of the formate/​bicarbonate couple is the solubility of the corresponding salts. For example, the molar solubilities (mol salt in 100 mL H 2 O, 20 °C) of formate salts based on different cations are ranked in the following sequence: Rb + (4.25) > K + (4.01) > NH 4 + (2.26) > Cs + (2.14) > Na + (1.19) > Li + (0.76). , This solubility likely affects the amount of H 2 uptake and thereby is an important factor for the hydrogen density achievable for the overall reaction system.…”

Homogeneous Hydrogenation of CO2 and CO to Methanol: The Renaissance of Low‐Temperature Catalysis in the Context of the Methanol Economy

“…In alkaline medium, amines or alkali metal hydroxides react with CO 2 to form ammonium or metal salts of carbamate, bicarbonate or carbonates. [100,101] Such molecules can be catalytically hydrogenated to obtain methanol with three equivalents of H 2 . While reduction of CO 2 to methanol has also been achieved using other hydrogen sources including metal hydrides, boranes, silanes, water and others, molecular H 2 stands out as the most efficient, atom-economical, costeffective and industrially viable reductant, provided that appropriate infrastructure is available to handle H 2 under high pressures (Figure 4).…”

Versatile CO2 hydrogenation-dehydrogenation catalysis with Ru-PNP/ionic liquid system

“…The extreme simplicity and stability of the CO2/FA-based hydrogen storage system further underlines its viable implementation in hydrogen energy technologies. Accordingly, we present a catalytic system that can be applied directly for FA batteries based on reversible CO2 hydrogenation/FA dehydrogenation, 47 continuous H2 release from FA as LOHC, as well as a hydrogenative CO2 converter under energy-efficient conditions.…”